In recent years, there have been reports that magnetic domain walls driven by a current were observed in magnetic nanowires having submicron widths. Magnetic domain wall motion memories that are capable of moving magnetic domain walls by utilizing this effect have been suggested. In such a magnetic domain wall motion memory, magnetic nanowires (magnetic memory nanowires) each divided into magnetic domains are used, and information (data) “0” or “1” corresponding to the magnetization directions of the magnetic domain walls is stored. Since the magnetic domains move as the magnetic domain walls move when a current is applied, the information (data) stored in the magnetic domains also moves. Accordingly, the information can be read with a stationary sensor, and can be written with a stationary write unit. That is, the magnetic domain walls are equivalent to memory cells.
In general, there is an increasing demand for magnetic memories having larger capacities with higher cell densities, and there is also an increasing demand for reductions in power consumption.
Specific examples of write methods for the magnetic domain wall motion memories include: a write method utilizing a magnetic field that is generated around a wire different from the magnetic memory nanowires by applying a current to the different wire; a method of writing with spin transfer torque by utilizing magnetic tunnel junctions formed in some of the magnetic memory nanowires; and a write method by which a pair of pinning portions having opposite magnetization directions are provided for each magnetic memory nanowire and are located in the same plane as the magnetic memory nanowires, and magnetic domain walls are moved by applying a current to wires provided for the respective pinning portions. However, these write methods have yet to overcome the difficulties in lowering power consumption and increasing capacities. Therefore, there is still a demand for reductions in power consumption and writing with larger capacities.